Download DEFINITIONS

PHYSICS LECTURE EC – 2: ELECTROSTATICS
ELECTRIC FORCE
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Measurements of the velocity of the orbital electrons in an atom show the attractive force
between the electrons and the nucleus is stronger than the gravitational force between the two
objects.
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The attractive force between the electrons and the nucleus is called the ELECTRIC FORCE
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The electric force between charges may be calculated using Coulomb’s law.
qq 
Coulomb’s Law : Felectric  kc  1 2 2 
 r 
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o __________________________________________________________________
o There is an electrostatic force of attraction or repulsion between any two types of
charges located some distant apart.
o Electric force and charge are directly proportional
o Electric force and distance between charges is inversely proportional
o Coulomb’s constant kc = 8.9875 x 109 N·m2/C2
ELECTRIC FIELDS
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Electric field is defined as the electric force per unit charge.
The direction of the field is taken to be the direction of the force it would exert on a positive
test charge.
The electric field is radiated outward from a positive charge and radiated in toward a
negative point charge.
Electric field vector convention: ________________________________________________
Electric field strength depends on charge and distance.
q
E  kC 2
o
r
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PHYSICS LECTURE EC – 2: ELECTROSTATICS
ELECTRIC FIELD LINES
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Electric field line convention: __________________________________________________
The lines must begin on positive charges or at infinity (see first diagram above).
The lines must terminate on negative charges or at infinity (see second diagram above).
The number of lines drawn leaving a positive charge or approaching a negative charge is
proportional to the magnitude of the charge.
EXAMPLE 1:
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EXAMPLE 2:
No two field lines from the same field can cross each other.
OHM’S LAW
 The opposition to the motion of charge through a conductor is ________________________
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The work that must be performed against electric forces to move a charge between two
points is ____________________________________
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The rate at which charges pass through a given area is ______________________________
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Ohm’s Law: V = IR
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V: Potential Difference, I: Current, R: Resistance
____________________
____________________
EXAMPLE: The resistance of a steam iron is 19.0 . What is the current in the iron when it is
connected across a potential difference of 120 V?
G: _________________________
_________________________
U: _________________________
E: _________________________
S: _________________________
S: _________________________
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